1. Field of the Invention
This invention relates generally to the field of analog signal processing. More particularly, an impedance matching low noise amplifier having a bypass switch is provided that is especially well suited for use in a staged amplification system for a mobile communications device.
2. Description of the Related Art
The use of a low noise amplifier in a staged amplification system is known. One such amplification system is a cascading amplification system, commonly used in the receiver chain of mobile communication devices. A typical cascading amplification system utilizes at least two stages of amplification. Significantly, the first stage of amplification of the cascading amplifier critically affects the system noise figure because the noise output after the first stage is amplified by subsequent stages. For this reason, the first stage of a cascading amplification system typically consists of a low noise amplifier (xe2x80x9cLNAxe2x80x9d), which is characterized by a low noise figure.
An impedance matching low noise amplifier (xe2x80x9cLNAxe2x80x9d) having a bypassing switch includes an amplification circuit, a bypass switching network and a match adjustment circuit. The amplification circuit has an amplifier input and an amplifier output, and is configured to receive a radio frequency (RF) input signal at the amplifier input and apply a gain to generate an amplified RF output signal at the amplifier output. The bypass switching network is coupled to a low-gain control signal and is also coupled between the amplifier input and the amplifier output. The bypass switching network is configured to couple the amplifier input to the amplifier output when the low-gain control signal is enabled in order to feed the RF input signal through to the RF output signal. The match adjustment circuit is coupled to the low-gain control signal and the RF input signal, and is configured to couple the RF input signal to an impedance when the low-gain control signal is enabled.